In general, a method of forming a thin film on a wafer is classified into a physical vapor deposition (PVD) method employing a physical collision between particles such as a sputtering method and a chemical vapor deposition (CVD) method of forming the thin film on the wafer using a chemical reaction. The CVD method is more widely used since it is relatively excellent in terms of the uniformity of thin-film thickness and step coverage characteristics of the thin film as compared to the PVD method.
Now, a conventional CVD apparatus will be described hereinafter with reference to FIG. 1.
Referring to FIG. 1, the conventional CVD apparatus includes a chamber C where a deposition space of a wafer W is provided, a shower head for injecting a reaction gas into the chamber, and a heater H disposed within the chamber for heating the wafer W seated thereon so as to allow a thin film to be deposited on the wafer.
In case where a thin film is deposited on the wafer W, the heater H ascends. To this end, the heater H is raised and lowered, i.e., moved upwardly and downwardly by means of a feeding portion 30 having a feed screw.
Under the above construction, a thin film is deposited on the wafer W seated on the ascended heater H by means of a chemical reaction using a reaction gas.
However, in the CVD method, there has also occurred a problem in that when the flow of the reaction gas is in an unbalanced state within the reaction chamber, the thickness of the thin film being deposited on the wafer varies depending on respective positions over the whole surface of the wafer W, which leads to the formation of the thin film having uneven thickness over the whole wafer surface.